A Google search will give you a number of reasons. But a lot depends on the context: What do you mean by "succeed"? Do you mean it is widely adopted? Or do you mean profitable businesses formed around it? Or do you mean successfully deployed in a business? Or yet something else?
One reason, out of many, is the freedom and control it gave to the user of open source software. The transparency in an open source software development process enables all parties involved: developers, evaluators, users, contributors to make better decisions ultimately resulting in a successful software product.